The invention relates to a fuel injection system for an internal combustion engine with a fuel pump for supplying the fuel to a dual-fluid injector.
German Offenlegungsschrift DE-A 22 52 307 discloses a fuel injection system in which the fuel pump is a cam-operated injection pump which supplies fuel, at high pressure, to a dual-fluid injector in which water is introduced as an additional fluid. As soon as the fuel reaches the opening pressure of the nozzle needle of the dual-fluid injector, fuel and water are injected into the engine. Water is again introduced into the injector at a time when the pressure in the fuel supply line leading to the dual-fluid injector drops as a result of the return movement of the nonreturn valve disposed therein. As a result of the pressure drop, a specific quantity of water is sucked out of a water tank via a nonreturn valve into the fuel supply line and is mixed with the fuel therein for the next injection step. In the water-conducting supply line a shut-off or control valve is provided which opens or closes as a function of operating parameters of the internal combustion engine.
In this fuel injection system a quantity-controlling high-pressure piston injection pump is assigned to each dual-fluid injector.
It is the object of the present invention to provide a fuel injection system which permits the use of a simple feed pump and a simple structure for the introduction of the additional fluid. In addition, fuel should be supplied to a plurality of dual-fluid injectors utilizing only a single fuel pump.